1. Field of the Invention
The present invention relates to a data exchange apparatus for high-speed exchange of multimedia information such as sound, data and picture information.
2. Description of the Prior Art
FIG. 10 shows one example of the switching network of a typical conventional data exchange apparatus. The switching network shown in FIG. 10 is the so-called BANYAN network, which is one example of the system in which data is divided into predetermined units called packets and the header information of each packet is directly referred to by hardware means to thereby perform high-speed switching.
In the figure, the reference symbols a and b denote input packets, while the reference numeral 1 denotes incoming lines, 2 outgoing lines, and T denotes 2.times.2 unit switches.
In operation, each of the 2.times.2 unit switches T shown in FIG. 10 performs a switching operation in accordance with the state of the corresponding bit in the bit string constituting the header section of the input packet a. For example, each of the unit switches Ta that are arrayed in the first row from the left as viewed in FIG. 10 performs a switching operation such that, if the top bit in the header section is 0, the switch Ta couples the input line thereof to the upper output line thereof, whereas, if the top bit is 1, it couples the input line to the lower output line. The switches Tb that are arrayed in the second row from the left similarly perform a switching operation in accordance with the state of the second bit in the header section of the input packet a. If such unit switches are interconnected as shown in FIG. 10 and the number of a desired outgoing line 2 is expressed as a binary number and put to the top of the packet a, the packet a arrives at the desired outgoing line 2 no matter from which incoming line 1 it is inputted.
For example, assuming that the input packets a and b have "1001" as the number of a desired outgoing line 2, as shown in the figure, these packets a and b are always outputted to the one O.sub.9 of the outgoing lines 2 no matter from which incoming lines 1 they are inputted. The input packet a is outputted to the outgoing line O.sub.9 via the unit switches Te, Tg, Th and Ti, and the input packet b is similarly outputted to the outgoing line O.sub.9 via the unit switches Tf, Tg, Th and Ti.
The conventional data exchange apparatus having the above-described arrangement suffers, however, from the following problems. If packets a and b which are directed to the same one O.sub.9 of the outgoing lines 2, as in the case of FIG. 10, are simultaneously inputted to the incoming lines 1, blocking (collision) occurs at the unit switch Tg, resulting in either one of the packets a and b being lost. In addition, the prior art apparatus needs a high-speed memory in order to perform high-speed data exchange. Further, the conventional data exchange apparatus is adapted for individual packets and therefore arranged such that a packet which is inputted from one incoming line 1 is led to only one outgoing line 2 designated by the header. Accordingly, the prior art apparatus is incapable of satisfactorily functioning with respect to broadcasting packets which are each to be inputted from one incoming line 1 and led to a plurality of outgoing lines 2 simultaneously.